Method of compounding corrosion resisting forgeable ferrous alloys



Patented May 1, 1934 UNITED STATES 1,956,646 PATENT OFFICE METHOD OF COMPOUNDING CORROSION RESISTING F O R G E AB L E FERROUS ALLOYS No Drawing. Original application January 19,

1931, Serial No. 509,887. Divided and this application September 4, 1931, Serial No. 561,260

I 1 Claim.

My invention relates to a method of compounding forgeable chromium containing. corrosion resisting alloys of iron in such a way as to render such alloys free cutting without imparting to them 5 red shortness. In my copending application, filed January 19, 1931, Serial No. 509,887, of which this application is a division, I have described and claimed my invention of a forgeable corrosion resisting alloy of iron containing chromium rendered free cutting without imparting to it red shortness by the incorporation in the alloy of diffused particle of molybdenum sulphide and my present invention is of a method by means of which an alloy of this character and of the highest characteristics can be prepared.

My invention may be usd in compounding chromium containing forgeable alloys of iron of any usable character and combination and consists in incorporating in a melted bath of such an alloy sulphur in excess of any such percentage as would combine with the manganese constituent of the alloy and molybdenum in sufficient quantity to insure its combination with the excess sulphur. The sulphur and molybdenum must of course be thoroughly diffused through the melted bath, as a result of which molybdenum, by reason of its strong afllnity for sulphur will react with any eutectic forming sulphides formed by the union of the sulphur with the iron constituent of the alloy, with formation and precipitation in the bath of exceedingly fine particles of molybdenum sulphide, uniformly and thoroughly distributed throughout the mass of the'al- 10y. In practice the excess sulphur ismost con- 35 veniently added to the bath in the form of iron I sulphide, which will readily difiu'se itself throughout the bath and the necessary molybdenum is most advantageously added in the form of ferro molybdenum, which will also readily-difiuse itself through the bath, though the molybdenum may also be added to the bath in the form of a molybdenum salt, of which calcium molybdate is the most available, such salts being at once decomposed by the heat of the bath, so that the molybdenum is free to combine with the iron and difiuse itself throughout the bath so that the molybdenum will react with the iron sulphide in the formation of precipitated particles of molybdenum sulphide.

In practicing my process I haveincorporate'd sulphur in the bath in the manner described, in percentages of from .08 to .25 and I have incorporated molybdenum in the manner dscribed in percentages of from .25 to .50. The reactive percentages of molybdenum and sulphur are of course well known and will of course determine the theoretical percentage of molybdenum necessary to combine with the sulphur constituent of the alloy but to insure a substantial elimination of iron sulphide from the alloy it is advisable to use molybdenum in excess of the theoretical combining ratio with sulphur, which can be done without disadvantage, as molybdenum is in itself a not undesirable constituent element of such alloys.

A typical alloy which I have prepared by my described process, which is forgeable without red shortness and highly corrosion resistance and has also the quality of free cutting, shows by analysis the following composition:

Carbon .21

Manganese .20

Phosphorus .010

Sulphur .120 gravimetric Sulphur .040 volumetric Silicon .18

Nickel .06

Chromium 12.73 Molybdenum .31

Obviously the toughness of any particular alloy in the absence of the molybdenum sulphide constituent and the degree to which it is desired to impart free cutting qualities to any particular alloy will determine the percentage of excess sulphur and of molybdenum to be added to the melted bath for the production therein of precipitated particles of molybdenum sulphide in such percentage as will give the desired result.

It will be understood by those skilled in the art that my invention relates to that class of so called stainless steels which derive their corrosion resisting qualities from their incorporation of chromium in sufiicient quantity, not less than 7%, to impart what is known as stainless characteristics to the steel, and that my process is usefully applicable in the compounding of all such stainless steels as, for example, in the compounding of the difi'erent classes of stainless steel described in ,Steel and its Heat Treatment by Bullens, third edition, published 1927,.in New York, chapter on stainless steel, pp. 280 to 292.

It is well known that stainless steels not infrequently incorporate certain generally minor percentages of other ingredients than chromium, manganese, and sulphur, such, for example, as tungsten, copper, silicon, vanadium, cobalt, nickel and zirconium, and it will be understood that I do not intend to exclude such possible alloying elements from the scope of my claim.

which consists in diffusing iron sulphide through-' out a melted bath of such an alloy by incorporating in the bath sulphur in excess of such quantity as will unite with any manganese pres= ent in the bath, said sulphur being present in percentage between .07 and 2% and also diffusing throughout the bath molybdenum in sufiicient quantity to react with substantially all of the sulphur of the iron sulphide by adding to the bath molybdenum in excess of the quantity required to bring about this reaction and in percentage between .10 and 5% and, the balance of the said alloy steel being substantially iron, thereby effecting in the bath a reaction between the molybdenum and the sulphur combined with iron and the precipitation throughout the bath of finely divided particles of molybdenum sulphide with substantial elimination of iron sulphide.

FREDERICK C. LANGENBERG. 

